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ILMC Conference
Paper:
Battery Design for
Cleaner Production
Third APRCP
Conference, Manila
February 28 - March
2, 2000
Early Beginnings
The International Lead
Management Center is based in North Carolina, USA and is made up of a
consortium of ten of the leading mining and smelting companies in the world.
Its mission is to promote and implement lead risk reduction practices within
the industry and amongst the general population worldwide through
multi-stakeholder pilot program activities.
The battery in
automobiles today is far removed from the first lead-acid storage batteries
developed in 1859 by Gaston Planté for use in telegraph equipment and I
doubt that he could have envisaged the impact of his invention on our lives
today. Simply put, our 21st century life-style would not be possible without
lead-acid batteries. The first cells to look like our modern day batteries were
invented in 1866 by G Leclanché of France. In his design and some of the
most modern batteries, the electrolyte is “gelled”. The first
accumulator plates similar to type used in the modern lead-acid battery were
conceived in 1881 by Henri Tudor. Interestingly, the experimental industrial
version of the accumulator designed by Tudor worked for 16 years without
interruption and only recharged from dynamo driven by a water-wheel.
Whilst many will insist
that the chemistry of the modern battery has changed little since the late
1890’s, what has changed in the intervening years is the technology
applied to the materials, the advanced production methods and our concern and
care for the environment and human health. Indeed, the lead acid battery is
likely to change more in the next decade than in the last 100 years.
The Amazing Voltaic
Battery
I suppose the
industries’ long association with the lead-acid battery goes back to those
pioneering mining companies of the late 1800’s. At that time the most
dangerous job in the mining industry was “Blasting”. Fuses were
somewhat unpredictable and often failed to ignite the charge of dynamite. Or
worse still, seemed to fail to ignite the charge, only to explode without
warning, killing anyone in close proximity to the blast.
Salvation, however, was
at hand with the application of “Voltaic” Battery technology. The
introduction of electrical detonation for explosive charges truly
revolutionized “blasting” practices throughout the mining industry.
As the graphic suggests, the lead acid battery brought about an
“amazing” transformation in mining practices and probably saved the
lives of many thousands of miners.
Nevertheless, it was the need to
incorporate a lead-acid battery into the automobile for “Starting”,
“Lights” and “Ignition”, the “SLI” battery, that
sealed the link between the lead industry and battery manufacture.
Indeed, today over 70% of World lead
production goes into lead acid battery manufacturing.
Lead Acid Batteries
Lead-acid batteries
either start or power cars, trucks, buses, boats, trains, rapid mass-transit
systems and recreational vehicles all over the globe. The car battery also
provides a stable electrical supply to a vehicle’s electrical system.
During power outages,
lead-acid batteries provide quiet, pollution-free emergency power for critical
operations such as air-traffic control towers, hospitals, railroad crossings,
military installations, submarines, and weapons systems. In these situations
the telephones stay on and this is because every major telephone company in the
world, including mobile telephone service providers, uses lead-acid batteries
as backup power to the telecommunications systems.
Were it not for standby
lead-acid batteries, we probably would have power outages nearly every day
because the electric utilities would not be able to handle rapid fluctuations
in the demand for electricity. This is when lead-acid batteries come to the
rescue, as enormous arrays of batteries delivering large amounts of electricity
for short periods of time until additional capacity is added to the grid.
Lead-acid batteries power electric fork trucks used in warehouses, factories,
mines, and ships. They also power the shuttle vehicles in airports, as well as
wheelchairs, amusement park shuttles and golf carts. On the road, lead-acid
batteries power electric law-enforcement vehicles, buses, and very soon mail
delivery vans.
The Legacy
For many years lead
acid battery manufacturing plants were regarded by many as sources of lead
contamination of the workforce, the general population and the environment. In
fact, only last year such a plant in Kosovo was shut down by the United Nations
because environmental experts thought the pollution levels around the site were
so high that there was a real risk of lead poisoning. This incident and others
have left the lead industry with an unenviable legacy.
Cleaner Battery Manufacturing
However, as more and
more new and modernized plants attain ISO 9002 for quality control, so we see a
steady improvement in environmental awareness and accordingly, an increasing
number of battery manufacturers applying for and achieving ISO 14001
accreditation for their Environmental Management Systems.
Last year, for example,
Philippine Recyclers Inc. based in Manila were awarded ISO 14001 certification
to become the first Secondary Lead Plant in Asia to hold both ISO 9002 and
14001 accreditations.
But the key question
for us today is why recycle the spent batteries?
Why Recycle?
Indeed, unless we
recycle the spent batteries they will literally be falling about our ears, but
apart from the inconvenience, recycling:
Saves Natural
Resources
By making products from
recycled materials instead of virgin materials, we conserve land and reduce the
need to mine for more minerals.
Saves Energy:
It takes less energy to
make a recycled battery. In fact secondary lead bullion, for example, requires
four times less energy to make than primary lead.
Saves Clean Air and
Water:
In most cases, making
products from recycled materials creates less air pollution and water pollution
than making products from virgin materials.
Saves Landfill
Space:
When the materials that
you recycle go into new products, instead of landfills or incinerators,
landfill space is conserved.
Saves Money and
Creates Jobs:
The recycling industry
and the associated processes create far more jobs than landfill sites or waste
incinerators, and recycling is frequently the least expensive waste management
option for cities and towns.
Recycling Loop
The earth’s
resources, no matter how abundant we think they are, are finite, and precious
to all of us. It is essential that the food we eat, the water we drink and the
air we breathe are free of toxins and keep us healthy. Maintaining a clean
environment, re-using and reclaiming resources benefits us all. Moreover, sound
environmental management will support sustainable development and growth.
It is therefore in
everybody’s interest to recycle as much scrap material as possible,
especially lead acid batteries, because if they are not recycled the materials
in the battery pose a serious environmental problem and a threat to human
health.
The ideal loop would be:
- Lead bullion production
- Battery manufacture
- Recovery and recycling of the
battery materials
Lead acid batteries, in
whatever form, are all recyclable to a lesser or greater extent. This only
means, however, that a battery can be recycled after it is spent. The battery
itself does nothing to close the recycling loop if it is not recycled, but you,
your governments and your industries can ensure that they enter the loop by
creating an infrastructure that will promote and facilitate recycling.
Battery Components
In order to ensure that
the loop is closed we not only need the right infrastructure, but we also need
a battery that is made up of recyclable materials. The modern Lead acid battery
is made up of:
- A resilient plastic container that
is usually polypropylene, but increasingly is made from alternative co-polymers
or reinforced, but the case material can also be metallic or a synthetic
rubber.
- Positive and negative internal lead
plates. The positive electrode (cathode) typically consists of pure lead
dioxide supported on a metallic grid, whereas the negative electrode (anode)
consists of a grid of metallic lead alloy containing various elemental
additives that includes one or more of the following and sometimes others not
mentioned, antimony, calcium, arsenic, copper, tin, strontium, aluminum,
selenium and more recently bismuth and silver. These alloying elements are used
to change grid strength,Positive and negative internal lead plates. The
positive electrode (cathode) typically
- Porous synthetic plate separators
are increasingly made from rib-reinforced polyethylene, but are also available
in PVC and fiber-glass.
- The plates are immersed in a liquid
electrolyte consisting of 35% sulfuric acid and 65% water. It is the
electrolyte that facilitates the chemical reactions that enable the storage and
discharge of electrical energy and permit the passage of electrons that provide
the current flow.
- The positive and negative lead
terminals used to connect the battery to the car and pass the current from the
individual cells via a series of connecting lugs and bridges.
Separator
Inside the battery, the
pasted positive and negative plates must be separated to prevent short
circuits. This separation is achieved using thin sheets of porous and synthetic
insulating material used as spacers between the positive and negative plates.
Fine pores in the separators allow electrical current to flow via the
electrolyte and between the plates while preventing short circuits. The battery
is made up so that a positive plate is paired with a negative plate and a
separator. This unit is called an element, and there is one element per battery
cell, or compartment inside the battery case.
The separator is a very
important component of the modern lead acid battery and has been the subject of
much intensive research.
The average composition
of the lead battery varies around the world, but consists of approximately 25%
metallic lead, 50% lead sulfate/oxide, 15% acid, 5% plastics, and the balance
made up from other materials and residuals (mainly silica used to bulk up the
separators).
All the components of
the modern lead acid battery should be recyclable, but the design of some
batteries means that certain components cannot be recovered for economic
reasons or interfere with the recovery process.
Recycling Rates
As nearly all the
components of the modern lead acid battery are recyclable, from an Industry
perspective lead-acid batteries are an environmental success story because in
the United States just over 96% is recovered and in most of the G7 nations
upwards of 95% is recycled. Compared to the usual “flagship” recycled
products such as glass bottles at only 38%, aluminum cans at nearly 64% and
newsprint at about 68%, lead acid batteries are the clear leaders in the field.
In fact, used lead-acid batteries have topped the list of the most highly
recycled consumer products for over a decade.
Unfortunately, battery
recycling is not a public utility and scrap batteries are only recycled because
it is profitable for the secondary non-ferrous industry to do so. In recent
years, however, the introduction of essential environmental and occupational
health regulations, and an all time low lead price has cut profit margins to
such an extent that most secondary lead smelters that are not the beneficiaries
of government levies are barely breaking even and others have closed due to
severe losses.
It is increasingly
important therefore for the secondary lead industry to generate as much income
from a spent battery as possible in order to improve margins and maintain
profitability.
Although there are some
BAT listed processes that smelt whole batteries most modern secondary plants
break spent batteries in a mechanical hammer-mill and gravity separate the
components in a series of water filled tanks.
Recycling Options
The washed and dried
polypropylene pieces are sent to a plastic recycler, where the chips are melted
and extruded to produce plastic pellets for use in the manufacture of battery
cases.
Although certain
processes will combine the waste lead streams, the most efficient plants feed
the paste to the smelting furnace to recover soft lead and the grids and
terminals are sent to a melting furnace for the production of hard lead. Lead
bullion from both sources will be refined, cast into ingots and sold to the
battery manufacturer. The soft lead is suitable for battery paste and the hard
lead bullion ideal for grids and terminals.
Polyethylene separators
can be separated from the polypropylene waste stream and recycled, although in
most secondary plants the current practice is to use this waste as a fuel
supplement.
Used battery acid can
be handled in four ways:
- Neutralized, and the resulting
effluent treated to meet clean water standards and then released into the
public sewer system.
- Reclaimed and after topping up with
concentrated acid then used as the electrolyte in new batteries
- Chemically treated and converted to
either agricultural fertilizer using ammonia or to powered sodium sulfate for
use in either glass and textile manufacturing or as a filler or stabilizer in
household laundry detergent.
- Converted to gypsum for use in the
production of cement or by the construction industry in the manufacture of
fiber-board.
The Ideal Design
With recycling rates
for used batteries as high as 96% you might think that that the industry
already has a consistent design that is ideal, but unfortunately this is not
the case.
Plastic Case
Material
Washed polypropylene
chips from used battery cases are worth about US$300 per ton and provide
valuable additional income for the recycler. Increasingly, however, battery
case material is being produced from a range of cheaper durable plastics that
are impossible to separate economically from the polypropylene, thereby rending
the plastic chips valueless and only fit to use as fuel. The next generation of
batteries will demand a more rigid case material, so there is now an ideal
opportunity for the industry to use the same plastic material in order to
maximize recovery and reuse. Accordingly, rubber and metallic case material
could be phased out except for instances where there is a specific need in
which case the design should be such that it is easy to dismantle the battery.
Acid Electrolyte
Increasingly over the
years the users of lead acid batteries are demanding gelled electrolyte to
reduce the risk of acid leakage and spillage. Furthermore, spirally wound
batteries require the gelled electrolyte. The gelled electrolyte is difficult
to remove from the battery paste prior to smelting and those secondary plants
that delsulfurize prior to smelting will have to equip themselves to deal with
the increase in sulfur dioxide production and remove it from the waste gas
stream prior to discharge to the atmosphere.
Lead Plates
New battery designs
that increase power, reliability and extend battery life, in particular the
valve regulated battery designs, demand the use of soft very pure lead for the
grids. Whilst the use of pure lead in this instance eases recycling, the vast
majority of batteries consumed are standard automotive SLI batteries requiring
stronger grids that can only be made from lead alloys. Many of these alloys
have traditionally been made from elements that are either toxic,
environmentally undesirable or contaminate the secondary bullion. In order for
secondary lead producers to compete with primary lead and command the best
premiums, the recycled lead must be of a quality suitable for the formation of
lead oxide, used in the production of battery paste.
Increasingly battery
manufacturers are moving towards the use of elements, such as calcium and tin,
not only because they enhance performance, but because they are generally
easier to recycle and remove from the lead bullion during the refining stage.
Such elements are also desirable because they are not toxic and do not threaten
the environment. Further research is required in this area, but is seems likely
that a combination of traditional pyro-metallurgical smelting and the emerging
hydro-metallurgical recycling will enable the secondary industry to produce a
very pure lead bullion economically and with improved environmental performance
due to lower emission levels and waste residues.
Battery Paste
Current formulations
for battery paste are ideal for the secondary industry and the likely changes
on the horizon do not change this position in the near future.
Lead Terminals
The lead terminals
are not critical to the chemical efficiency of the battery and only provide the
link to complete the electrical circuit. Consequently the terminals are often
made from a low quality lead bullion and while this might minimize costs, if
the bullion used to produce the terminals contains other elements that are
either toxic or undesirable, these elements will add a further refining burden
and potential occupational safety hazard to the recycler. Ideally, the
terminals should be made from lead refined to the London Metals Exchange (LME)
standard for 99.97% bullion to minimize contamination
Plate Separators
In the early days of
battery manufacturing, the plate separators were made of wood. Today, they are
produced from a multitude of plastics, paper and glass fiber. Whilst
glass-fiber presents some separation and wear problems in the mechanical
battery breakers, it does not present an environmental threat apart from adding
to the inert slag burden. Virtually all of the plastic and paper separators are
impossible to recycle economically and are really only suitable as a fuel
supplement. Certain plastic separators, however, such as PVC (polyvinyl
chloride) cannot be burnt as fuel because an acidic gas is generated and there
is the potential for the production of dioxins. Without an economic method to
segregate PVC from the other separators, the whole of the separator waste
stream is destined for landfill.
The Way Forward
In order to reduce the
pollution caused by standing traffic, particularly in large cities, 36 volt
electrical systems will shortly be installed as standard in all new cars. This
higher voltage will enable instant start/stop motoring and automatically switch
off the engine when the car is not moving. However, such a battery that enables
an instance start when the accelerator is engaged will weigh approximately 40
kilos, that is three times the weight of the average 12 volt SLI battery. With
such an increase in battery size anticipated, battery design will be critical
to maintaining sound environmental performance throughout the clean production
life cycle.
As we see the way
forward, there should be an improved dialogue between the battery manufacturers
and the secondary lead industry, so that by sharing their respective
experiences and needs, lead acid batteries will be designed in way that not
only improves the electrical performance of the battery, but throughout the
recycling loop generates a real and sustainable improvement in recycling and
environmental performance. Indeed, many of you already benefit from established
schemes that perpetuate high rates of recycling, competitive pricing and lower
energy consumption by the secondary industries. Furthermore, if batteries are
designed to maximize recycling as well as energy storage and power output, then
the “cradle to grave” philosophy can be realized and lead acid
batteries will look a very attractive proposition compared with other
technologies.
Information
For further information
about Battery Recycling and/or Lead Risk Reduction programs please contact ILMC
by e-mail at: mail@ilmc.org.
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ILMC wish to thank
Paul Frost of Britannia Refined Metals for his contribution towards the
preparation of this paper. |